Respiratory Risks from Occupational Fluoride Exposure

Fluoride Action Network | 2008 | By Michael Connett

Starting in the 1930s, scientists have observed that workers exposed to airborne fluorides suffer from an elevated rate of respiratory disorders. For over 50 years, however, US government and industry scientists made repeated assurances that the allowable level of fluoride dusts and gases in industrial workplaces would not cause any ill effect to respiratory function. These claims proved to be incorrect, fatally so, with countless workers in U.S. industries suffering painful, debilitating lung disease as a result.

Epidemiological Studies

As documented in the studies cited below, a vast body of epidemiological and experimental research has proven that allowable levels of fluoride in the workplace is hazardous to lung function, increasing the risk of several respiratory disorders including asthma, bronchitis, and emphysema. For many workers, the fluoride-induced damage to lung function persists long after they cease working.

While workers in industry are often exposed to multiple air contaminants, the epidemiological studies have repeatedly found that fluoride dusts and gases (at levels as low as 0.05 mg/mg3) are the key irritants responsible for the high rate of respiratory illness among fluoride-exposed workers. Fluoride’s risk to respiratory function is independent of the risk from smoking, but the combination of fluoride exposure and smoking presents a risk greater than either factor by itself.

Controlled Human Experiments

In an attempt to further determine whether airborne fluoride can directly damage lung function, a series of well-controlled experiments have exposed healthy human volunteers to varying levels of airborne fluoride. These studies have repeatedly found that concentrations (as low as 0.05 mg/m3) of fluoride considered “safe” by US government scientists can impair lung function within just 1 to 2 hours of exposure.

ATSDR Admits that Allowable Level of Fluoride in Air from 1940s-2000s Was Toxic

Based on this new research, the US Agency for Toxic Substances and Diease Registry (ATSDR) recently estimated that the safe level of airborne fluoride exposure (0.02 mg/m3) should be 125 times lower than the currently allowable levels in US workplaces (2.5 mg/m3). Nevertheless, the National Institute for Occupational Safety and Health (NIOSH) continues to maintain its outdated, and dangerous, standard.

The Beryllium Fluoride Factor

In addition to fluoride’s ability, in and of itself, to damage respiratory function, it has also been clearly established that fluoride exacerbates the respiratory damage associated with beryllium exposure — and vice versa. Thus, workers exposed to both beryllium and fluoride dusts will suffer more serious effects, at lower concentrations, than workers exposed to either chemical by itself. Read more.

1. Epidemiological Studies of Industrial Workers:

“In conclusion, potroom asthma appears to occur in the United States at the studied aluminum smelters. There was a significant statistical relationship between the incidence of asthma and the mean gaseous fluoride exposure in the study population, whereas the relationship between asthma incidence and the other contaminants was less significant.”
SOURCE: Taiwo OA, et al. (2006). Incidence of asthma among aluminum workers. Journal of Occupational and Environmental Medicine 48(3):275-82

A 7-yr study was conducted to evaluate the respiratory effects of fluorine compounds on exposed workers in a small-scale enamel enterprise. Air monitoring was done and 75 pairs, exposed and non-exposed workers were examined… The values of fluorine in the air of workplaces ranged from 0.1 to 3.7 mg/m3 air during the study… Linear regression analysis has shown positive correlations between the fluorine exposure and incidence of chronic bronchitis (r=0.75), as well as the incidence of chronic respiratory diseases (r=0.71). Fluorine exposure may be responsible for the high incidence of chronic irritative respiratory diseases, especially for chronic bronchitis in exposed workers. For diseases prevention it is advisable to reduce the levels of fluorine in the air of workplaces…”
SOURCE: Viragh E, et al. (2006). Health effects of occupational exposure to fluorine and its compounds in a small-scale enterprise. Industrial Health 44(1):64-8.

“Welders inhale gases and respirable particles. To investigate the relationship between fluoride exposure and respiratory symptoms in welders using basic electrodes containing calcium fluoride, 63 railroad track welders were interviewed. Fluoride was measured in post-shift urine samples. Seventeen welders reported respiratory symptoms related to welding fume exposures. Respiratory symptoms were somewhat more common with increasing concentrations of fluoride in urine. The association between welding fume exposure and respiratory symptoms seems related more to fluorides than to other particles among welders using basic electrodes… Some salts of fluorides have been associated with an increased occurrence of asthma. Asthma is more common among welders. This study adds arguments for studying the occurrence of asthma among welders exposed to fluorides.”
SOURCE: Sjögren B. (2004). Fluoride exposure and respiratory symptoms in welders. International Journal of Occupational and Environmental Health 10:310-2.

“OBJECTIVES: To determine whether exposure to five different occupational substances contributes to respiratory symptoms in aluminium smelter workers. METHODS: A cross-sectional survey of 1,615 male employees of two Australian aluminium smelters was conducted in 1995… CONCLUSIONS: This study suggests that the relevant causative agents for respiratory symptoms in aluminium smelters are fluoride and inspirable dust.”
Fritschi L, et al. (2003). Respiratory symptoms and lung-function changes with exposure to five substances in aluminium smelters. International Archives of Occupational and Environmental Health 76(2):103-10.

“Occupational asthma is the principal respiratory health problem within the primary aluminium industry. Current evidence indicates that it is irritant induced and due to occupational exposure to the inhalation of gaseous or particulate fluoride compounds.”
SOURCE: O’Donnell TV. (1995). Asthma and respiratory problems–a review. The Science of the Total Environment 163(1-3):137-45.

“The relation between plasma fluoride levels and bronchial responsiveness was investigated in a longitudinal study in aluminium potroom workers who reported work-related asthmatic symptoms… A positive association was found between bronchial responsiveness and plasma fluoride levels, such that an increase in the plasma fluoride level of 10 ng/ml was associated with an increase in the dose-response slope by a factor of 1.11 (95% confidence interval 1.05 to 1.17)… Bronchial responsiveness in aluminium potroom workers reporting work-related asthmatic symptoms appears to be related to plasma levels of fluoride.”
SOURCE: Kongerud J, et al. (1994). Aluminum potroom asthma: the Norwegian experience. European Respiratory Journal 7(1): 165-172.

“In a survey of 370 aluminium potroom workers in western Norway, bronchial responsiveness, lung function, and respiratory symptoms were studied in relation to occupational exposure to air contaminants in the potroom. Increased prevalences of respiratory symptoms, work related asthmatic symptoms, and abnormal lung function were found in subjects exposed to total fluorides above 0.5 mg/m3 when compared with workers exposed to total fluorides at concentrations of less than 0.5 mg/m3… These findings indicate that work related asthmatic symptoms in potroom workers may be related to exposure to fluorides.”
SOURCE: Soyseth V, Kongerud J. (1992). Prevalence of respiratory disorders among aluminum potroom workers in relation to exposure to fluoride. British Journal of Industrial Medicine 49: 125-130.

“Epidemiological studies of aluminum potroom workers have been in progress in Norway since 1986. The occurrence of work-related asthmatic symptoms and their determinants were studied. Work-related asthmatic symptoms and airflow limitation were closely associated with duration of potroom employment. A significant relationship between current fluoride exposure and work-related asthmatic symptoms was observed in a smaller, cross-sectional population where a detailed exposure classification was carried out.”
SOURCE: Kongerud J. (1992). Respiratory disorders in aluminum potroom workers. Med Lav 83(5): 414-417.

“The influence of occupational work exposure and host factors on the incidence of dyspnea and wheezing as reported in questionnaires was examined in 1,301 new employees in aluminum electrolytic potrooms…In 523 subjects who were assigned to specific levels of exposure at the end of follow-up, a dose-response gradient was found between the development of symptoms and fluoride exposure. Increased risk with increasing amounts of tobacco was also observed, but childhood allergy and a family history of asthma were not significantly related to the outcome variable… The proportional hazard regression analysis showed that smoking and total fluoride exposure were the most important predictors of development of dypsnea and wheezing. The risk among smokers was two to three times that of nonsmokers, and exposure to fluorides higher than 0.4 mg/m3 increased the risk of symptoms three to five times than that in the low-exposure group… During the years of our study the exposure for all job categories was well below the 1.0 mg/m3 hygienic standards for fluorides… We conclude that current total fluoride exposure and smoking are the major risk factors for development of dypsnea and wheezing in aluminum potroom workers.”
SOURCE: Kongerud J, Samuelsen SO. (1991). A longitudinal study of respiratory symptoms in aluminum potroom workers. American Review of Respiratory Disease 144: 10-16.

“The respiratory symptoms and ventilatory lung functions of the production-line workers (F-exposed) at an aluminum plant in China have been studied. The data were compared with those obtained from the office workers (controls). F-exposed groups had a higher prevalence of respiratory symptoms than controls and their complaints of phlegm were significantly increased in the older subjects. Whereas several cases of chronic bronchitis were observed in the F-exposed groups, none could be found in the controls. The expiratory flow rate at 25% of the vital capacity/height (V25/HT), which is sensitive in the detection of small airway obstruction, was decreased.”
SOURCE: Tatsumi M, et al. (1991). Health Survey of Workers of an Aluminum Plant in China. III. Respiratory symptoms and ventilatory functions. Fluoride 24(3): 90-94.

“[W]e found no pathology in our aluminum smelter workers other than movement restrictions and cases of asthmoid bronchitis.”
SOURCE: Runge H, Franke J. (1989). Radiological modifications of the skeletal system among aluminum smelter workers: A 15 year retrospective study. Fluoride 22: 157-164.

“In the present study, 1-hour exposure to HF (hydrogen fluoride) did not result in an acute inflammation in the lung 2 hours after the end of the exposure period, as assessed through the pattern of cells and mediators in BAL fluid. In contrast, the numbers of neutrophils and lymphocytes were reduced after HF exposure, as were the concentrations of a range of soluble components. We have earlier demonstrated that the same HF exposure is capable of inducing an airway inflammation with a lymphotic infiltration 24 hours after exposure. Moreover, this is accompanied by neutrophil activation and MPO release. Additionally, we have confirmed that HF induces an inflammatory response in the nasal epithelium within 1.5 hours after exposure.”
Lund K, et al. (2005). Inflammatory markers in bronchoalveolar lavage fluid from human volunteers 2 hours after hydrogen fluoride exposure. Human & Experimental Toxicology 24:101-8.

“The development of asthmalike symptoms among aluminum potroom workers has been associated with exposure to fluorides. In the present study, the immediate nasal response in humans was examined subsequent to short-term hydrogen fluoride (HF) exposure. Ten healthy subjects were exposed to HF (3.3-3.9 mg/m(3)) for 1 h. Nasal lavage (NAL) was performed before, immediately after, and 1.5 h after the end of exposure. Control lavages were performed on the same subjects at the same time points but without HF exposure. At the end of HF exposure, 7 of 10 individuals reported upper airway symptoms… In conclusion, exposure to HF induced immediate nasal inflammatory and antioxidant responses in healthy human volunteers. These findings may contribute to a further understanding of the way HF exerts damage to the airways and show that HF could represent an occupational hazard.”
SOURCE: Lund K, et al. (2002). Human exposure to hydrogen fluoride induces acute neutrophilic, eicosanoid, and antioxidant changes in naval lavage fluid. Inhalation Toxicology 14(2): 119-132.

“Asthma is known as a major health problem in primary aluminum production. Epidemiologic studies have demonstrated associations between fluoride exposure and asthmatic symptoms among potroom workers… The aim of our present study was to test the hypothesis that hydrogen fluoride may cause an inflammatory cell response in the human respiratory tract, as reflected in changes in lymphocytes, CD3 positive cells, and neurophils in BAL fluid… Our study shows that the exposure of healthy subjects to hydrogen fluoride concentrations above 0.6 mg/m3 can induce an inflammatory response in the airways. The inflammatory response appeared primarily as a relative increase in lymphocytes, especially CD3-positive cells… It is of interest that the acute inflammatory response due to hydrogen fluoride exposure was found at conentrations that can occur in the atmosphere of the primary aluminum industry.”
SOURCE: Lund K, et al. (1999). Increased CD3 positive cells in bronchoalveolar lavage fluid after hydrogen fluoride inhalation. Scandinavian Journal of Work, Environment, and Health 25(4): 326-34.

“20 healthy, male volunteers were exposed for one hour to constant HF concentrations that ranged from 0.2 to 5.2 mg/m3; these concentrations are known to occur among potroom workers in the primary aluminium industry… Upper airway and eye symptoms occurred after one hour of exposure to HF even when below the Norwegian hygienic standard for fluorides… A significant decrease was found in FVC (Forced Vital Capacity) in the group exposed to fluorides below the hygienic standard (n = 9) and for the entire group (n = 23)… There was a significant correlation between symptom scores of the upper airways and the concentration of HF as well as changes in plasma fluoride (Delta C) and maximum concentrations of plasma fluoride (Cmax, table 3). A significant correlation was also found between the total symptom score for airways and HF concentrations, Delta C and Cmax. Scores from the eyes and lower airway symptoms were not correlated with any of the exposure variables… Exposures above 2.5 mg/m3 were associated with pronounced symptoms from the upper respiratory tract…. Most of the symptoms which were reported came from the upper airways. This is in line with findings from both animal and human studies… The symptoms of the lower respiratory tract were mainly coughing and expectoration. As HF is a highly water soluble gas, it is remarkable that lower respiratory symptoms occurred at low exposures… According to our findings, the concentrations of HF should be kept well below 2.5 mg/ml to avoid symptoms of the upper airways and eyes.”
SOURCE: Lund K, et al. (1997). Exposure to hydrogen fluoride: an experimental study in humans of concentrations of fluoride in plasma, symptoms, and lung function. Occupational and Environmental Medicine 54: 32-37.

3. Animal Experiments:

“This unique dog study by Davis et al. expands the understanding of chronic fluoride poisoning by inhalation. It… documented that inhaling fluoride caused pulmonary cellular alterations, which recent studies have linked to a diminished ability to cope with infectious bacteria. Finally, the Davis et al. study followed the year-long progression of fluoride-induced inflammation in the lungs, a process observed in current studies as starting in humans when they inhale fluoride for as little as one hour. In general, past and present studies converge as to the type of respiratory damage caused by fluoride, inflammation and emphysema, and the current research serves as a confirmation of the work that was performed decades earlier but never published.”
SOURCE: Mullenix PJ. (2005). Fluoride poisoning: a puzzle with hidden pieces. International Journal of Occupational and Environmental Health 11(4):404-14.